A method for manufacturing a titanium oxide-containing slag whereby iron is separated from an ore, such as ilmenite, including titanium oxide and iron oxide is known. As exemplified in FIG. 4, ilmenite and a carbonaceous reductant (for example, coke or charred coal) are fed to a submerged arc furnace (hereinafter referred to as SAF) 9 through a feeding line of materials 1 and a feeding line of carbonaceous reductant 2, respectively with controlling each of the feed rates by a regulating unit for feed rate 3. The iron oxide is reduced and melted. Molten iron is then tapped, and titanium oxide-containing slag is tapped from an output port disposed at the furnace wall.
Methods described below are known in the art. In a method, ilmenite is mixed with a carbonaceous reductant such as coke and a small amount of calcium oxide flux, and then the mixture is agglomerated. The resultant mixture is charged in an electric furnace and is heated, thereby separating molten iron and molten titanium oxide-containing slag.
In another method, a required amount of molten iron is stored in a melting furnace, and a carbonaceous material, such as coke, pitch, or heavy oil is added to the molten iron bath, while blowing with oxygen, thereby evaporating the carbonaceous material. Simultaneously, titanium raw material such as magnetite sand or titaniferous iron ore is charged in the iron bath. Metal oxides such as iron oxide and chromium oxide in the titanium raw material are selectively reduced, thereby increasing the content of titanium oxide in a slag and concentrating the titanium oxide.
In the conventional method wherein separation of the iron and the titanium oxide-containing slag is performed by reduction and melting the iron oxide in a raw material using a melting furnace such as the SAF, the temperature in the furnace drops due to the action of the reductive reaction of the iron oxide, which is an endothermic reaction. Thus, a large quantity of electric power is required to keep the furnace temperature constant. Furthermore, a large amount of molten FeO is generated during the process. The molten FeO seriously damages refractories in the furnace; therefore, it is difficult to manufacture the titanium oxide-containing slag efficiently using the SAF. In addition, the furnace has to be kept in a highly reducing atmosphere so as to reduce the iron oxide. Unfortunately, the titanium oxide is also reduced in the reducing atmosphere.